Status: New Owner: ---- Labels: Type-Defect Priority-Medium
New issue 109 by jonkande...@gmail.com: CogVM crashes with simple code http://code.google.com/p/cog/issues/detail?id=109
Below are a few lines of code that crashes the CogVM on both Linux and Windows. File-in the Smalltalk code below, then evaluate [nil crashCogVM]. The code uses [1-1] but it could use [1+1] or [56+98]. I put the code on nil, but that is not important either. I think the important thing is that the primitive (+ or -) is evaluated but the result is not assigned into any variable. Also important is that the code is put into a loop that I assume has been JIT optimized. The image I used is Pharo 1.4 one-click with latest update #14459. This code does not crash StackVM.
!UndefinedObject methodsFor: 'crash' stamp: 'JonKAnderson 11/29/2012 17:26'! crashCogVM " Evaluate [ nil crashCogVM ]"
| i | i := 20. 1 to: i do: [:d | 1-1 ] ! !
Updates: Status: Fixed Owner: eliot.miranda@gmail.com Labels: -Priority-Medium Priority-High
Comment #1 on issue 109 by eliot.miranda@gmail.com: CogVM crashes with simple code http://code.google.com/p/cog/issues/detail?id=109
OK, this is fixed. Thanks, Jon. The bug was that the pop of the folded constant did not record the implicit send in the folding, hence pc mapping was wrong. i.e. 1-1 gets folded away to 0, and the code generator marks the result 0 as being the result of a send, but then the result gets discarded (when it is popped) without being noted in the pc map. In the machine code there needs to be at least a nop generated, and in the map there needs to be an entry, to correspond to the send of +, so that when machine code pcs are mapped to bytecode pcs there are the correct number of entries in the map. In the above case, the VM converts the interpreted frame to a machine code frame (coincidently) on the 20th iteration and needs to map the bytecode pc to the correct machine code pc to continue in machine code. But because of the missing entry in the map for 1-1, the pc mapping machinery answered 0, and the VM ended up jumping into the void.
Comment #2 on issue 109 by jonkande...@gmail.com: CogVM crashes with simple code http://code.google.com/p/cog/issues/detail?id=109
Great! That was fast. -Jon
thanks!
On 2012-12-01, at 11:10, cog@googlecode.com wrote:
Comment #2 on issue 109 by jonkande...@gmail.com: CogVM crashes with simple code http://code.google.com/p/cog/issues/detail?id=109
Great! That was fast. -Jon
Updates: Status: Done
Comment #3 on issue 109 by esteba...@gmail.com: CogVM crashes with simple code http://code.google.com/p/cog/issues/detail?id=109
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